Exemplary embodiments of the present invention relate to a method for assembling an engine module for a motor vehicle engine, which comprises a cylinder head cover and a camshaft rotatably mounted in the cylinder head cover.
In order to reduce assembly outlay when assembling a motor vehicle engine and to reduce storage and logistics costs in engine assembly, engine modules that are already fully assembled are supplied directly to the assembly line of automotive manufacturers by suppliers. Such engine modules consist of, for example, a cylinder head cover and a camshaft mounted therein. In the context of engine assembly, only this module then has to be attached to the cylinder head of the engine.
European Patent Publication No. EP 1 155 770 B1 describes a method for assembling an engine module consisting of a cylinder head cover and a camshaft mounted therein. A cylinder head cover is provided having lead-throughs, through which the cylindrical support shaft of the subsequent camshaft is inserted. The components, such as e.g. the cams, which are to be attached to the camshaft must be disposed in specific receptacles such that they are positioned precisely in the required angular orientation and at the required axial position. If the cylinder head cover and the components to be attached to the support shaft with their lead-throughs for receiving the support shaft are aligned with respect to each other at the correct position and angle, then the support shaft is pushed through the lead-throughs. In accordance with one embodiment of the method described in EP 1 155 770 B1, the components to be attached to the support shaft are heated before the support shaft is pushed through, and the support shaft is cooled in order to ensure force-free insertion of the support shaft. The cams are attached to the support shaft by means of a press-fit connection. EP 1 155 770 B1 describes various ways of producing this press-fit connection. The press-fit connection can be produced by virtue of the fact that the support shaft is inserted by means of a press by the application of force. Another way of producing the press-fit connection resides in the fact that the inserted support shaft is subjected to hydroforming so that the outer diameter of the shaft is widened consecutively or simultaneously at least in the region of the components.
The method disclosed in EP 1 155 770 B1 is complex and associated with high costs because the components that are to be attached to the support shaft have to be precisely positioned and aligned, even before insertion of the support shaft, in the manner how they are to be disposed on the subsequent camshaft. In order to achieve this, specifically designed and formed holding elements are required, into which the components can be inserted at the correct position and angle. For each component, the holding element must have a specifically formed holding receptacle. The production of these holding elements is complex and expensive. Moreover, different holding elements are required for different camshafts. The reason for this is the angular alignment of the cams relative to the support tube of the camshaft is, for example, dependent upon whether it is a camshaft for a 4-cylinder engine or a 6-cylinder engine.
Exemplary embodiments of the present invention are directed to a method for assembling an engine module consisting of a cylinder head cover and a camshaft, in which no specifically designed devices are required for holding and arranging the components, which are to be attached to the support shaft, in the correct angular position in each case, and which can be used in a flexible manner for different camshafts which have cams with different angular positions.
A significant advantage of the method in accordance with the invention resides in the fact that the components, such as e.g. cams, sensor wheels etc., which are to be attached to the support shaft, are positioned, prior to insertion of the support shaft, merely at those axial positions that do not correspond to the axial positions occupied by these components on the fully constructed camshaft. Therefore, the components do not need to be precisely aligned with regard to their angular position relative to the support shaft. In the case of the method in accordance with the invention, precise alignment of the components prior to insertion of the support shaft can be completely omitted. Therefore, no specific holding devices are required which, even before insertion of the support shaft, serve to fix the precise angular position of the individual components, which are to be attached to the support shaft, relative to the support shaft.
In accordance with the present invention, after insertion of the support shaft the components are attached thereto by virtue of the fact that either the components are pressed onto the widened-diameter portions of the support shaft allocated thereto or the widened-diameter portions allocated to the components are pressed into the lead-through openings of the components. The respective angular position of each individual component relative to the support shaft can be conveniently adjusted by virtue of the fact that the support shaft is rotated relative to the respective component about a specific angle, so that the required relative angular position of the component with respect to the support shaft is achieved. Therefore, the method in accordance with the invention can be used to construct different modules with completely different camshafts, without a specific holding device being required in each case for each different camshaft, in order to ensure the correct positioning and alignment of the cams on the support shaft. Therefore, by means of the method in accordance with the invention, it is possible in a cost-effective and convenient manner to manufacture, for different engines or engine variants, modules having different camshafts, in which the components to be attached to the camshaft are disposed in different angular positions relative to the support shaft.
In accordance with one embodiment of the invention, the widened-diameter portions are introduced into the support shaft by means of a mechanical forming method, such as e.g. roller-burnishing.
In accordance with the invention, the bearing receptacles of the cylinder head cover and the bearing portions of the support shaft are dimensioned such that, when the cylinder head cover is in the fully mounted state, the bearing receptacles together with the bearing portions form sliding bearings. The bearing portions of the support shaft can be ground to size such that, in the cooled state, the support shaft has the slightly smaller diameter-required for formation of a sliding bearing—than the bearing receptacle of the cylinder head cover.